Convergence deflecting device for single-gun, plural-beam color picture tube

ABSTRACT

In a color picture tube of the single-gun, plural-beam type in which a central beam and two side beams originate in a common horizontal plane and are all made to pass through the center of an electron lens for focussing the beams on the color screen with the central beam emerging from the lens along the optical axis of the latter and the side beams emerging from the lens along paths that are oppositely divergent from the axis, the divergent side beams are acted upon by an electrostatic convergence deflecting device constituted by pairs of horizontally spaced plates arranged along the divergent paths and having voltages applied thereacross to produce electric fields by which the divergent side beams passing therethrough are deflected to converge at a common spot with the central beam on the apertured grill or mask associated with the screen, and a main deflection yoke produces magnetic fields by which the beams are deflected horizontally and vertically, respectively, for causing the beams to scan the screen; the horizontal distances between the plates of each pair are varied in the vertical direction from a maximum at the common horizontal plane to minimums at the opposed edges of the plates remote from such common plane so as to correspondingly vary the strengths of the electric fields and thus correct distortions in the rasters of the side beams.

United States Patent [191 Miyaoka et al.

[ Dec. 11, 1973 CONVERGENCE DEFLECTING DEVICE FOR SINGLE-GUN, PLURAL-BEAM COLOR PICTURE TUBE 175] Inventors: Senri Miyaoka, Kanagawa; Minoru Morio, Tokyo, both of Japan [73] Assignee: Sony Corporation, Tokyo, Japan [22] Filed: June 8, 1971 [21] Appl. No.: 151,003

Related US. Application Data [62] Division of Ser. No. 813,827, April 7, 1969, Pat. No.

[52] US. Cl. 315/13 C, 313/78 [51] Int. Cl. H01j 29/50 [58] Field of Search 313/78, 80, 70 C; 315/113 C [56] References Cited UNITED STATES PATENTS 3,467,881 9/1969 Ohgoshi et a1. 315/13 C 3,513,350 5/1970 Ohgoshi et a1. 315/13 C 3,448,316 6/1969 Yoshida et al. 315/13 C 3,432,711 3/1969 Clayton 313/80 2,403,239 7/1946 Rose 313/78 Primary Examiner--Carl D. Quarforth Assistant Examiner-J. M. Potenza Attorney-Lewis H. Eslinger, Alvin Sinderbrand and Curtis, Morris & Safford {57] ABSTRACT In a color picture tube of the single-gun, plural-beam type in which a central beam and two side beams originate in a common horizontal plane and are all made to pass through the center of an electron lens for focussing the beams on the color screen with the central beam emerging from the lens along the optical axis of the latter and the side beams emerging from the lens along paths that are oppositely divergent from the axis, the divergent side beams are acted upon by an electrostatic convergence deflecting device constituted by pairs of horizontally spaced plates arranged along the divergent paths and having voltages applied thereacross to produce electric fields by which the divergent side beams passing therethrough are deflected to converge at a common spot with the central beam on the apertured grill or mask associated with the screen, and a main deflection yoke produces magnetic fields by which the beams are deflected horizontally and vertically, respectively, for causing the beams to scan the screen; the horizontal distances between the plates of each pair are varied in the vertical direction from a maximum at the common horizontal plane to minimums at the opposed edges of the plates remote from such common plane so as to correspondingly vary the strengths of the electric fields and thus correct distortions in the rasters of the side beams.

3 Claims, 8 Drawing Figures PAIENTED DEC 1 I I975 3. 7 78 686 SENRI MI YAOKA MINORU MORIO ATTORNEY This application is a division of our copending application Ser. No. 813,827, filed Apr. 7, 1969, now U.S. Pat. No. 3,619,687 and having a common assignee herewith.

Thisinvention relates generally to color picture tubes of the single-gun, pluralbeam type, and particularly to tubes of that type in which the plural beams are passed through the optical center of a common electron lens by which the beams are focussed on the color phosphor screen.

In single-gun, plural-beam color picture tubes of the described type, for example, as specifically disclosed in U.S. Pat. No. 3,448,316, issued June 3,1969, and having a common assignee herewith, three laterally spaced electron beams are emitted by a beam generating or cathode assmebly and directed in a common substantially horizontal plane with the central beam coinciding with the optical axis of the single electron focussing lens and the two outer or side beams being converged to cross the central beam at the optical center of the lens and thus emerge from the latter along paths that are divergent from the optical axis. Arranged along such divergent paths are respective pairs of convergence deflecting plates constituting a convergence deflecting device and having voltages applied thereacross to produce electric fields which laterally deflect the divergent beams in a substantially horizontal plane for causing allbeams to converge at a common spot on the apertured beamselecting grill or shadow mask associated with the color screen. Further, arranged between the convergence deflecting device and the screen is a main deflection yoke which, in response to its reception of horizontal and vertical sweep signals, produces horizontal and vertical magnetic deflection fields acting on all of the beams to cause the latter to scan the color screen in predetermined rasters. Since the beams are horizontally spaced and non-parallel during their passage through the horizontal deflection field, the distances that the side beams travel through such field will be respectively greater and less than the distance that the central beam travels through the field when the beams are deflected toward one side or the other side of the screen. If the horizontal deflection field has a uniform flux density thereacross, the side beam traveling therethrough for the greater distance will be deflected to a greater extent than the side beam traveling the shorter distance through the field and misconvergence of the beams will result. Even if the horizontal deflection field is given a non-uniform flux density thereacross, misconvergence of the beams can be thereby avoided only when the beams are deflected toward one side or the other of the screen midway between the top and bottom of the screen, that is, when the common plane of the beams passing through the horizontal deflection field is directed horizontally, that is, substantially perpendicular to the vertical lines of magnetic flux of the horizontal deflection field. However, when the common plane of the beams passing through the horizontal deflection field is substantially inclined from the horizontal, that is, when the vertical deflection field deflects the beams to cooperate with the horizontal deflection field in directing the beams toward an upper or lower corner of the screen, the difference between the distances traveled by the side beams through the horizontal deflection field is further increased and hence may not be compensated by the non-uniform flux density established across the horizontal deflection field. Thus, the rasters of the side beams may have shapes that are oppositely distorted with respect to the shape of the raster of the central beam.

Accordingly, it is an object of this invention to provide a single-gun, plural-beam color picture tube in which the rasters of the several beams are free of distortion with respect to each other.

Another object is to provide a single-gun, plural- V beam color picture tube in which distortions of the rasters of the several beams are avoided by a particular construction of the convergence deflecting device.

In accordance with an aspect of the invention, the described distortions of the rasters of the side beams with respect to the raster of the central beam are avoided by suitably varying, in the direction perpendicular to the common plane in which the beams originate, the dis tances between the paired plates of the convergence deflecting device, whereby to correspondingly vary the strengths of the electric fields between such plates by which the side beams are convergently deflected.

The above, and other objects, features and advantages of this invention, will be apparent in the following detailed description of illustrative embodiments which is to be read in connection with the accompanying drawing, wherein:

FIG. 1 is a schematic sectional view in a horizontal plane passing through the axis of a single-gun, pluralbeam color picture tube of the type to which this invention is preferably applied;

FIG. 2 is a diagrammatic view to which reference is hereinafter made in explaining the invention;

FIG. 3 is a diagrammatic view showing the possible relative distortions of the rasters of the several beams, as seen from the viewers side of the tube screen, and which are to be avoided by this invention;

FIG. 4 is a diagrammatic, transverse sectional view through the convergence deflecting device of a color picture tube according to a first embodiment of this invention; and

FIGS. 5-8 are views similar to FIG. 4, but showing other embodiments of the invention.

Referring to the drawings in detail, and initially to FIG. 1 thereof, it will be seen that a single-gun, pluralbeam color picture tube of the type to which this invention may be applied comprises a glass envelope (indicated in broken lines) having a neck N and cone C extending from the neck to a color screen S provided with the usual arrays of color phosphors S S and S and with an apertured beam selecting grill or shadow mask G p. Disposed within neck N is an electron gun A having cathodes K K and K each of which is constituted by a beam-generating source with the respective beamgenerating surfaces thereof disposed as shown in a plane which is substantially perpendicular to the axis of the electron gun A. In the embodiment shown, the beam-generating surfaces are arranged in a straight line so that the respective beams B 8,; and B emitted therefrom are directed in a substantially horizontal plane containing the axis of the gun, with the central beam B being coincident with such axis. A first grid G is spaced from the beam-generating surfaces of cathodes K K and K and has apertures g 3 and g formed therein in alignment with the respective cathode beam-generating surfaces. A common grid G is spaced from the first and grid G and has apertures g g and g formed therein in alignment with the respective apertures of the first grid 6,. Successivelygarranged in the axial direction away from the common grid G are open-ended, tubular grids or electrodes G G, and G respectively with cathodes K K and K grids G, and G and electrodes G G and G being suitably maintained in the depicted, assembled positions thereof.

For operation of the electron gun A of FIG. 1, appropriate voltages are applied to the grids G and G and to the electrodes 6;, G and 6,. Thus, for example, a voltage of to minus 400V is applied to the grid G a voltage of 0 to 500V is applied to the grid G a voltage of 13 to 20KV is applied to the electrodes G and G and a voltage of 0 to 400V is applied to the electrode 6,, with all of these voltages being based upon the cathode voltage as a reference. As a result, the voltage distributions between the respective electrodes and cathodes, and the respective lengths and diameters thereof, may be substantially identical with those of a unipotential-single beam type electron gun which is constituted by a single cathode and first and second, singleapertured grids. 7

With the applied voltage distribution as described hereinabove, an electron lens field will be established between grid G and the electrode G to form an auxiliary lens L as indicated in dashed lines, and an electron lens field will be established around the axis of electrode G.,, by the electrodes G G, and G to form a main lens L, again as indicated in dashed lines. In a typical use of electron gun A, bias voltages of 100V, 0V, 300V, 20KV, 200V and 20V may be applied respectively to the cathodes K K and K the first and second grids G, and G and the electrodes G G and G Further included in the electron gun A of FIG. 1 and electron beam convergence deflecting means F which comprise inner shielding plates P and P disposed in the depicted spaced, relationship at opposite sides of the gun axis, and axially extending, deflector plates Q and Q which are disposed, as shown, in outwardly spaced, opposed relationship to shielding plates P and P, respectively. Although depicted as substantially straight, it is to be understood that the deflector plates Q and Q may, alternatively, be somewhat curved or outwardly bowed, as is well known in the art.

The shielding plates P and P are equally charged and disposed so that the central electron beam B will pass substantially undeflected therebetween, while the deflector plates Q and Q have negative charges with respect to the plates P and P so that electron beams B and B will be convergently deflected as shown by the respective passages thereof between the plates P and Q and the plates P and Q. More specifically, a voltage V which is equal to the voltage applied to the electrode G may be applied to both shielding plates P and P, and a voltage V which is some 200 to 300V lower than the voltage V is applied to the plates Q and Q to result in the plates P and P being at the same potential, and in the application ofa deflecting voltage difference or convergence deflecting voltages V between the plates P and Q and the plates P and Q and it is, of course, this convergence deflecting voltage V which will impart the requisite convergent deflection to the electron beams B and B In operation, the electron beams B 8 and B which emanate from the beam generating surfaces of the cathodes K K and K will pass through the respective grid apertures g g and g,,,, to be intensity modulated with what may be termed the red, green and blue intensity modulation signals applied between the said cathodes and the first grid G The electron beams will then pass through the common auxiliary lens L to cross each other at the center of the main lens L. Thereafter, the central electron beam 8 will pass substantially undeflected between sheilding plates P and P since the latter are at the same potential. Passage of the electron beam B between the plates P and Q and of the electron beam B between the plates P and Q will, however, result in the convergent deflections thereof as a result of the convergence deflecting voltage V applied therebetween, and the system of FIG. 1 is so arranged that the electron beams B B and B will desirably converge or cross each other at a common spot centered in an aperture of the beam selecting grill or mask G so as to diverge therefrom to strike the respective color phosphors of a corresponding array thereof on screen S. More specifically, it may be noted that the color phosphor screen S is composed of a large plurality of sets or arrays of vertically extending red, green and blue phosphor stripes or dots S S and S with each of the arrays or sets of color phosphors forming a color picture element. Thus, it will be understood that the common spot of beam convergence corresponds to one of the thusly formed color picture elements.

The voltage V may also be applied to the lens electrodes G and G and to the screen S as an anode voltage as well as to the aperture grill G,,. Electron beam scanning of the face of the color phosphor screen is effected in conventional manner, for example, main deflection yoke means indicated in broken lines at D and which receives horizontal and vertical sweep signals to produce horizontal and vertical deflection fields by which the beams are made to scan the screen for providing a color picture thereon. Since, with this arrangement, the respective electron beams are each passed, for focussing, through the center of the main lens L of the electron gun A, the beam spots formed by impingement of the beams on the color phosphor screen S will be substantially free from the effects of coma and/or astigmatism of the same main lens, whereby improved color picture resolution will be provided.

In the color picture tube as illustrated on FIG. 1, plates P and P and plates Q and Q are shown flat and parallel with each other so that the electric fields between plates P and Q and plates P and Q are substantially uniform thereacross, that is, in the direction perpendicular to the common horizontal plane of beams B B and B Thus, as the beams are vertically deflected by the vertical deflection field of yoke D so as to be directed at the upper or lower portions of screen S and such vertical deflection field vertically displaces the beams within convergence deflecting device F, the deflecting effects on beams B and B of the fields between plates P and Q and plates P and Q, respectively, are substantially unchanged. However, as shown on FIG. 2, when the horizontal deflection field of yoke D deflects the beams toward the left side of the screen as seen from the viewers side of the latter, that is, downwardly asviewed on FIG. 2, the side beams 13,, and B travel distances through such horizontal deflection field that are respectively greater than and smaller than the distance that the central beam B travels through the horizontal deflection field. Conversely, when the horizontal deflection field of yoke D deflects the beams toward the right side of the screen as viewed from the viewers side, the distances traveled by the beams B and B through the horizontal deflection field are respectively smaller than and greater than the distance that the central beam B travels through such field. By reason of the foregoing differences between the distancesthat the beams travel through the horizontal deflection field when deflected by the latter toward one side or the other'of the screen S, the raster of beam B and the raster of beam B would be displaced toward the left and toward the right, respectively, from the raster of the beam B as seen from the viewers side of the screen. If the horizontal deflection field of yoke D is given a non'uniform flux density thereacross, for example, a greater flux density at the sides than at the middle of the field, the described relative displacements of the rasters can be compensated for so long as the common plane of the beams is substantially horizontal, that is, so long as the beams are directed at the screen substantially midway between the top and bottom of the screen. However, when the horizontal deflection field of yoke D directs the beams toward one side or the other of the screen at a time when the vertical deflection field of yoke D deflects the beams vertically so that the common plane of the beams is substantially inclined from the horizontal to direct the beams toward a corner of the screen, the differences between the distances traveled by the beams through the horizontal deflection field are further increased, as compared with the differences in the distances traveled through the field when the common plane of the beams is horizontal, so that even the mentioned non-uniform flux density across the horizontal deflection field of yoke D would be ineffective to avoid distortions of the rasters of beams B and 8,, relative to the raster of beam 8 Assuming that the raster of central beam B has a rectangular shape, as indicated at L on FIG. 3, the rasterL of bcamB as seen from the viewers side of the screen, is distorted in the sense that its sides are convex toward the right, while the raster L of beam B is oppositely distorted, that is, its sides are convex toward the left.

In accordance with the present invention, such distortions of the rasters of side beams B and B relative to the raster of central beam B are avoided by suitably varying, in the direction perpendicular to the common plane in which the beams originate, for example, in the vertical direction for the tube of FIG. 1, the distances by which plates P and Q and plates P and Q are spaced from each other. For example, in theembodiment shown by FIG. 4, plates P and P are made flat or planar while plates Q and Q are outwardly concave in the vertical direction or the direction across the plates, whereby the distances between plates P and Q and be tween plates P and Q are relatively small at the horizontal plane 21 containing the tube axis and such distances between the plates increase progressively in the direction of vertical plane 22 upwardly and downwardly from horizontal plane 21 in which the beams all originate.

Since convergence deflecting device F is disposed adjacent the main deflecting yoke D (FIG. 1), it will be apparent that the vertical deflection field of yoke D will extend into device F, and thereby influence the vertical positions of the beams B B and 8,, in passing through device F. Thus, when the vertical and horizontal deflection fields of yoke D are effective to direct the beams toward a corner of the screen, the vertical deflection field of yoke D will vertically displace beams B B and B either upwardly or downwardly from plane 21 within convergence deflection device F. By reason of the increased distance betweeen plates P and Q and plates P and Q at such displaced positions of beams B and B the parts of the electric fields then acting on such beams will be of relatively reduced intensity thereby to similarly reduce the convergent deflections imparted to beams B and B Thus, for example, when the beams are horizontally and vertically deflected by yoke D so as to be directed at the upper or lower lefthand corner of the screen, as seen from the viewers side thereof, the left-ward deflection of beam 8,; by the field between plates P and Q will be reduced and the right-ward deflection of beam B by the field between plates P and Q will be similarly reduced, whereby to bring the left-hand sides of the rasters L and L,,, as seen on FIG. 3, into agreement with the left-hand side of the raster L Similarly, when the beams are horizontally and vertically deflected by yoke D so as to be directed at the upper or lower right-hand corner of the screen as viewed on FIG. 3, the left-ward and rightward deflections of beams B and B respectively, by the fields between plates P and Q and plates P and Q will be reduced whereby to bring the right-hand sides of rasters L and L into agreement with the right-hand side of raster L Thus, distortions of the rasters L and L relative to the raster L can be effectively avoided by suitably selecting the position of convergence deflecting device F relative to yoke D and the shapes of plates 0 and Q.

As shown on FIGS. 5 and 7, the effect described above may also be achieved by providing flat or planar outer plates Q and Q and outwardly convex inner plates P and P (FIG. 5), or by providing outer plates Q and Q that are inwardly convex and inner plates P and P that are outwardly convex (FIG. 7). In each of these modifictions, the distances between plates P and Q and between P and Q vary from a minimum at the horizontal plane passing through the tube axis to maximums at the upper and lower portions of the plates to conversely vary the strengths of the electrical fields between plates P and O and plates P and Q. Since plates P and P are at equal potential there is no electric field established therebetween, and thus the varying distance between plates P and P in FIGS. 5 and 7 does not affect beam B as the latter is vertically deflected.

Of course, in the foregoing, it has been assumed that the distortions of rasters L and L relative to raster L that are to be corrected are those shown on FIG. 3. However, a situation may arise, for example, by reason of a particular configuration of the horizontal deflection field produced by yoke D, in which the raster of beam B has the shape indicated at L on FIG. 3 while the raster of beam 8,; has the shape indicated at L In the latter case, the plates P and Q and the plates P and Q are shaped so that the distances therebetween are maximum at the horizontal plane containing the axis of the tube and decrease progressively therefrom in the vertical direction, that is, in the direction perpendicular to the common plane in which the beams originate. In achieving such variations in the distances between the plates, plates P and P may be flat or planar and plates Q and Q may be outwardly convex (FIG. 6), or plates P and P may be inwardly convex and plates Q and Q may be outwardly convex (FIG. 8).

Further, in each of the above described embodiments of this invention, the convergence deflection device F consists of only a single pair of plates P and Q or P and Q acting on each of the beams B and B to deflect the respective beam in the direction for convergence with the central beam B However, the invention can also be appiied to color picture tubes, for example, as disclosed in the copending U.S. application Ser. No. 718,738, filed Apr. 4, 1968, and having a common assignee herewith, in which the beams following paths diverging from the tube axis upon emerging from the focussing lens are each successively acted upon by two pairs of deflecting plates, with the first pair of plates establishing an electric field therebetween by which the respective beam is further diverged from the tube axis and the second pair of plates establishing a field therebetween by which the beam is deflected in the direction for converging with the other beams. The foregoing arrangement makes it possible to increase the angles of incidence of the side beams 13,; and B at the beam selecting apertured grill or mask G whereby to permit a decrease in the distance of the latter from screen S for facilitating the accurate locating and mounting of the grill or mask G relative to the screen S. Where each of the side beams 13,, and B is successively acted upon by two pairs of deflecting plates, as aforesaid, one or the other of such pairs of plates, and preferably the pair of plates closest to the location of the main deflection yoke, is provided with a distance between the plates that varies in the direction perpendicular to the common plane in which the beams originate so as to avoid distortion of the raster of the respective beam in accordance with this invention.

Having described various embodiments of this invention, it is to be understood that the invention is not limited to those precise embodiments, and that various changes and modifications may be effected therein by one skilled in the art without departing from the scope or spirit of the invention.

What is claimed is:

1. A single-gun, plural-beam color picture tube comprising a colorscreen, beam generating means directing a central beam and two side beams in a common horizontal plane toward said screen, electron lens means defining a focusing field having a center through which the beams pass and by which the bundle of electrons in each of the beams are focused on said color screen with the central beam emerging from said lens along the optical axis of the latter and said two side beams emerging from said lens along paths that are oppositely divergent from said central beam, electrostatic convergence deflecting means including a pair of horizontally spaced plates arranged along each of said divergent paths, said spaced plates of each pair being disposed at the inside and outside, respectively, of the side beam in the related divergent path and having voltages applied thereacross to produce an electric field by which the respective side beam passing therethrough is deflected horizontally to converge at a common spot with said central beam and the other of said side beams, and a main deflection yoke producing magneticfields by which said beams are deflected horizontally and vertically respectively, for causing the beams to scan said screen and produce respective rasters on the latter; said convergence deflecting means being located within the field produced by said yoke to deflect said beams vertically so that said beams are similarly deflected vertically within said convergence deflecting means, and the horizontal distance between said plates of each of said pairs varying progressively in the vertical direction normal to said common horizontal plane from a maximum at said common horizontal plane to minimums at the opposed edges of the plates remote from said common plane so as to correspondingly vary the strength of the respective electric field for changing the rasters of said side beams with respect to the raster of said central beam and thereby compensating for deviations between said rasters as produced by said magnetic fields of the main deflection yoke.

2. A single gun, plural-beam color picture tube according to claim 1, in which the inner plate of each of said pairs which is closest to said central beam is flat, and the other plate of the respective pair is convex at the side thereof facing away from said inner plate.

3. A single-gun, plural-beam color picture tube according to claim 1, in which the plates of each of said pairs are convex at the sides thereof facing away from each other. 

1. A single-gun, plural-beam color picture tube comprising a color screen, beam generating means directing a central beam and two side beams in a common horizontal plane toward said screen, electron lens means defining a focusing field having a center through which the beams pass and by which the bundle of electrons in each of the beams are focused on said color screen with the central beam emerging from said lens along the optical axis of the latter and said two side beams emerging from saiD lens along paths that are oppositely divergent from said central beam, electrostatic convergence deflecting means including a pair of horizontally spaced plates arranged along each of said divergent paths, said spaced plates of each pair being disposed at the inside and outside, respectively, of the side beam in the related divergent path and having voltages applied thereacross to produce an electric field by which the respective side beam passing therethrough is deflected horizontally to converge at a common spot with said central beam and the other of said side beams, and a main deflection yoke producing magnetic fields by which said beams are deflected horizontally and vertically respectively, for causing the beams to scan said screen and produce respective rasters on the latter; said convergence deflecting means being located within the field produced by said yoke to deflect said beams vertically so that said beams are similarly deflected vertically within said convergence deflecting means, and the horizontal distance between said plates of each of said pairs varying progressively in the vertical direction normal to said common horizontal plane from a maximum at said common horizontal plane to minimums at the opposed edges of the plates remote from said common plane so as to correspondingly vary the strength of the respective electric field for changing the rasters of said side beams with respect to the raster of said central beam and thereby compensating for deviations between said rasters as produced by said magnetic fields of the main deflection yoke.
 2. A single gun, plural-beam color picture tube according to claim 1, in which the inner plate of each of said pairs which is closest to said central beam is flat, and the other plate of the respective pair is convex at the side thereof facing away from said inner plate.
 3. A single-gun, plural-beam color picture tube according to claim 1, in which the plates of each of said pairs are convex at the sides thereof facing away from each other. 